Compounds of the above formula, wherein at least one of R and R' is hydrogen, are disclosed in U.S. Pat. No. 3,767,805 or British Pat. No. 901,420 as intermediates in the preparation of ".alpha.-(cyclic tert. aminophenyl)-aliphatic acids" or "azo colouring matters" respectively. Surprisingly it was found that by properly selecting substituents and their relative positions within the aromatic nuclei of said dicarboximides, highly potent anticonvulsant agents are obtained.